- Although the flesh of the almaco jack is considered quality table fare, the species has been associated with ciguatera poisoning, a seldom fatal stomach irritation.
- The almaco jack is susceptible to tapeworm parasites in the caudal peduncle area, but the meat can be eaten safely if affected portions are cut away.
The swordfish has a large dorsal fin, no pelvic fins, and is generally characterized by the fusion and prolongation of the bones of the upper jaw to form a sword-like beak that constitutes one-third of the total body length. The body is elongated and slightly compressed. Coloration of the swordfish is variable, including black, grayish blue, brown, metallic purple or bronze. The body is dark above and pale below with no distinguishing bars or spots. The adult swordfish lacks both teeth and scales. The lack of bars (or stripes) and scales helps distinguish the swordfish from the striped marlin and other marlin.
The adult swordfish is an opportunistic feeder, preying primarily on squid but also other fish and crustaceans. The bill is often used to kill prey; the swordfish rises from beneath a school of fish, swinging the sword from side to side, then consuming the fish killed. Swordfish are primarily night feeders. They may either forage for smaller fish at the surface of the water or hunt larger prey at depths of 1,200 feet.
Swordfish occur worldwide in all tropical, subtropical and temperate waters of the Pacific, Atlantic and Indian Oceans, though their numbers and average size have decreased dramatically over the past 50 years. They prefer cooler waters in the northern and southern stretches of their range during warmer months and migrate toward tropical and subtropical waters in fall and winter.
Swordfish tend to concentrate along food-rich temperature fronts between cold and warm water masses, with migrations closely associated with surface temperatures between 75 and 84 F. There is some correlation between body size and the ability to tolerate cooler temperatures. While the larger fish may be found in areas where the surface temperature is as low as 50 F., and swordfish under 200 pounds are rarely found in water below 64 F. They are generally pelagic (roaming) fishes found in waters from 600 to 2,000 feet deep. The fish tend to swim alone or in small clusters of seven or less.
- The Latin name of the swordfish, xiphius gladius, is translated to gladiator of the sea, a fitting description for a fish that is the subject of most epic angling battles.
- Swordfish are known for their free jumping, also called breaching. It is thought by some researchers to be an effort to dislodge pests.